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Resultados 1101-1110 de 3,197
Nearshore dynamics of artificial sand and oil agglomerates
2015
Dalyander, P Soupy | Plant, Nathaniel G. | Long, Joseph W. | McLaughlin, Molly
Weathered oil can mix with sediment to form heavier-than-water sand and oil agglomerates (SOAs) that can cause beach re-oiling for years after a spill. Few studies have focused on the physical dynamics of SOAs. In this study, artificial SOAs (aSOAs) were created and deployed in the nearshore, and shear stress-based mobility formulations were assessed to predict SOA response. Prediction sensitivity to uncertainty in hydrodynamic conditions and shear stress parameterizations were explored. Critical stress estimates accounting for large particle exposure in a mixed bed gave the best predictions of mobility under shoaling and breaking waves. In the surf zone, the 10-cm aSOA was immobile and began to bury in the seafloor while smaller size classes dispersed alongshore. aSOAs up to 5cm in diameter were frequently mobilized in the swash zone. The uncertainty in predicting aSOA dynamics reflects a broader uncertainty in applying mobility and transport formulations to cm-sized particles.
Mostrar más [+] Menos [-]Hong Kong at the Pearl River Estuary: A hotspot of microplastic pollution
2015
Fok, Lincoln | Cheung, P.K.
Large plastic (>5mm) and microplastic (0.315–5mm) debris were collected from 25 beaches along the Hong Kong coastline. More than 90% consisted of microplastics. Among the three groups of microplastic debris, expanded polystyrene (EPS) represented 92%, fragments represented 5%, and pellets represented 3%. The mean microplastic abundance for Hong Kong was 5595items/m2. This number is higher than international averages, indicating that Hong Kong is a hotspot of marine plastic pollution. Microplastic abundance was significantly higher on the west coast than on the east coast, indicating that the Pearl River, which is west of Hong Kong, may be a potential source of plastic debris. The amounts of large plastic and microplastic debris of the same types (EPS and fragments) were positively correlated, suggesting that the fragmentation of large plastic material may increase the quantity of beach microplastic debris.
Mostrar más [+] Menos [-]Application of bias adjustment techniques to improve air quality forecasts
2015
Silibello, Camillo | D'Allura, Alessio | Finardi, Sandro | Bolignano, Andrea | Sozzi, Roberto
Two bias adjustment techniques, the hybrid forecast (HF) and the Kalman filter (KF), have been applied to investigate their capability to improve the accuracy of predictions supplied by an air quality forecast system (AQFS). The studied AQFS operationally predicts NO2, ozone, particulate matter and other pollutants concentrations for the Lazio Region (Central Italy). A thorough evaluation of the AQFS and the two techniques has been performed through calculation and analysis of statistical parameters and skill scores. The evaluation performed considering all Lazio region monitoring sites evidenced better results for KF than for HF. RMSE scores were reduced by 43.8% (33.5% HF), 25.2% (13.2% HF) and 41.6% (39.7% HF) respectively for hourly averaged NO2, hourly averaged O3 and daily averaged PM10 concentrations. A further analysis performed clustering the monitoring stations per type showed a good performance of the AQFS for ozone for all the groups of stations (r = 0.7), while satisfactory results were obtained for PM10 and NO2 at rural background (r = 0.6) and Rome background stations (r = 0.7). The skill scores confirmed the capability of the adopted techniques to improve the reproduction of exceedance events.
Mostrar más [+] Menos [-]Human and riverine impacts on the dynamics of biogeochemical parameters in Kwangyang Bay, South Korea revealed by time-series data and multivariate statistics
2015
The successful management of sustainable coastal environments that are beneficial to both humans and marine ecosystems requires knowledge about factors that are harmful to such environments. Here, we investigated seawater nutrient and carbon parameters between 2010 and 2012 in Kwangyang Bay, Korea, a coastal environment that has been exposed to intensive anthropogenic activities. The data were analyzed using cluster and factor analysis. We found that the biogeochemical cycles of nutrients and carbon were determined by river discharge into the bay and biological activity. However, the impacts of these factors varied both spatially and seasonally. During the past 10years, nutrient loads from the river and industrial complexes to the bay have decreased. The impacts of this decrease are visible in the phosphate concentration, which has fallen to a third of its initial value. We also examined the potential role of atmospheric nitrogen deposition in nitrogen cycling in the study area.
Mostrar más [+] Menos [-]Determination of mercury and vanadium concentration in Johnius belangerii (C) fish in Musa estuary in Persian Gulf
2015
Fard, Neamat Jaafarzadeh Haghighi | Ravanbakhsh, Maryam | Ramezani, Zahra | Ahmadi, Mehdi | Angali, Kambiz Ahmadi | Javid, Ahmad Zare
The main aim of this study was to determine the concentrations of mercury and vanadium in Johnius belangerii (C) fish in the Musa estuary. A total of 67 fishes were caught from the Musa estuary during five intervals of 15days in the summer of 2013. After biometric measurements were conducted, the concentrations of mercury and vanadium were measured in the muscle tissue of fish using a direct method analyzer (DMA) and a graphite furnace atomic absorption spectrophotometer, respectively. The mean concentration of mercury and vanadium in the muscle tissue of fish was 3.154±1.981 and 2.921±0.873mg/kg w.w, respectively. The generalized linear model (GLM) analysis showed a significantly positive relationship among mercury concentration, length, and weight (P=0.000). In addition, there was a significantly negative relationship between vanadium concentration and fish length (P=0.000). A reverse association was found between concentrations of mercury and vanadium. Mercury concentration exceeded the allowable standards of the Environmental Protection Agency (EPA), the World Health Organization (WHO), and the Food and Drug Administration (FDA) in J. belangerii (C).
Mostrar más [+] Menos [-]Seasonal and interannual variations in whole-ecosystem isoprene and monoterpene emissions from a temperate mixed forest in Northern China
2015
Bai, Jianhui | Guenther, Alex | Turnipseed, Andrew | Duhl, Tiffany
Contributed Measurements of BVOC emissions, meteorological parameters, and solar radiation were carried out in a temperate forest, China during the summer seasons in 2010 and 2011. Terpenoid emissions were measured using the Relaxed Eddy Accumulation (REA) technique on an above-canopy tower. Isoprene contributed 79.1% and 82.0% of terpenoid emissions in 2010 and 2011 summer. The monoterpene emissions were dominated by α–pinene, contributing 6.3% and 12.2% of the total terpenoid emissions in 2010 and 2011 summer. Terpenoid emissions exhibited strong diurnal variations. Isoprene and monoterpene emissions maxima typically occurred a few hours after the noon PAR peak and coincided with the daily temperature maximum. During 2011 summer, the mean isoprene emission flux (mg m–2 h–1) was 0.889, mean total monoterpene emission flux was 0.143. Emission factors, representing the emission expected at a temperature of 30 °C, for this site were 0.32mg m–2 h–1 for total monoterpenes and 4.3mg m–2 h–1 for isoprene. The observations were used to evaluate the isoprene and monoterpene emission magnitude and variability predicted by the MEGANv2.1 model. Canopy scale isoprene and monoterpene emission factors based on these observations fall within the range of emission factors assigned to locations within 50km of the site by the MEGANv2.1 emission model. When using the site specific landcover data for the site, the measured emission factors are 12% for isoprene and 20% for monoterpenes lower than the MEGANv2.1 emission factors. MEGANv2.1 predicts that variations in light intensity should result in significant changes in isoprene emissions during the study but this was not evident in the observations. Observed diurnal, seasonal and interannual variations in isoprene and monoterpene emissions were strongly correlated with air temperature which was the dominant driving variable for MEGANv2.1 during the study period. The observed temperature response for isoprene and monoterpenes is similar to the temperature sensitivity of the MEGANv2.1 response functions.
Mostrar más [+] Menos [-]The composition of PM1 and PM2.5 samples, metals and their water soluble fractions in the Bologna area (Italy)
2015
Sarti, Elena | Pasti, Luisa | Rossi, Mauro | Ascanelli, Monica | Pagnoni, Antonella | Trombini, Monica | Remelli, Maurizio
In this study the metal composition of PM1 and PM2.5 samples collected in the surroundings of a municipal incinerator located in a suburban–farming area, less than 10 km away from Northeast of Bologna (Italy) was investigated. Seven out of eight monitoring stations were installed in a domain of 8x9 km2 around the incinerator plant; the eighth station was placed inside the urban area of Bologna. The coordinates of four monitoring stations were selected on the basis of a preliminary study by using a dispersion model. Eleven metals (Al, Sb, As, Cd, Fe, Mn, Ni, Pb, Cu, V, Zn) were quantified in both the filter acid–digests and in the water extracts. The PM2.5 collected in all the sites of the domain were highly correlated with exception of the urban site. The daily average metal concentrations in summer were 1.84% and 1.14% for PM2.5 and PM1 respectively, indicating that fine particles are less enriched in metals. Fe, Al and Zn were the most abundant elements, and they represented about the 80% of the total amount of the analyzed ones. The average water soluble metal compositions were 0.71% and 0.41% for PM2.5 and PM1 respectively. In the sites of the suburban–farming studied area the Principal Component Analysis (PCA) and Cluster Analysis revealed differences between water soluble metal compositions in PM1 and PM2.5. The urban sites were characterized by lower total and soluble metals contents than the other PM2.5 stations installed around the incinerator plant. However, no noticeable difference in the concentrations of metals in the particulate matter between the sites chosen as maxima of incinerator emissions and the control sites was observed.
Mostrar más [+] Menos [-]A critical assessment of visual identification of marine microplastic using Raman spectroscopy for analysis improvement
2015
Lenz, Robin | Enders, Kristina | Stedmon, Colin A. | Mackenzie, David M.A. | Nielsen, Torkel Gissel
Identification and characterisation of microplastic (MP) is a necessary step to evaluate their concentrations, chemical composition and interactions with biota. MP ≥10μm diameter filtered from below the sea surface in the European and subtropical North Atlantic were simultaneously identified by visual microscopy and Raman micro-spectroscopy. Visually identified particles below 100μm had a significantly lower percentage confirmed by Raman than larger ones indicating that visual identification alone is inappropriate for studies on small microplastics. Sixty-eight percent of visually counted MP (n=1279) were spectroscopically confirmed being plastic. The percentage varied with type, colour and size of the MP. Fibres had a higher success rate (75%) than particles (64%). We tested Raman micro-spectroscopy applicability for MP identification with respect to varying chemical composition (additives), degradation state and organic matter coating. Partially UV-degraded post-consumer plastics provided identifiable Raman spectra for polymers most common among marine MP, i.e. polyethylene and polypropylene.
Mostrar más [+] Menos [-]Impact of deep-water fish farms on benthic macrofauna communities under different hydrodynamic conditions
2015
Valdemarsen, Thomas | Hansen, Pia Kupka | Ervik, Arne | Bannister, Raymond J.
In this study the environmental impacts of two fish farms located over deep water (180–190m) were compared. MC-Farm was located at a site with slightly higher water currents (mean current speed 3–5cms−1) than LC-farm (<2cms−1). Macrofauna composition, bioirrigation and benthic fluxes (CO2 and NH4+) were quantified at different stages of the production cycle, revealing very different impact of the two farms. Macrofauna abundance and bioirrigation were stimulated compared to a non-impacted reference site at MC-farm, while macrofauna diversity was only moderately reduced. In contrast, macrofauna communities and related parameters were severely impoverished at LC-Farm. This study suggests that deep-water fish farms should not be sited in low current areas (<2cms−1), since this will hamper waste dispersal and aggravate environmental impacts. On the other hand, fish farming at slightly more dynamic sites can lead to stimulated benthic macrofauna communities and only moderate environmental impacts.
Mostrar más [+] Menos [-]Polycyclic aromatic hydrocarbons in surface sediment from Yangpu Bay, China: Distribution, sources and risk assessment
2015
Li, Ping | Diao, Xiaoping | Zhang, Yu | Xie, Yanli | Yang, Fei | Zhou, Hailong | Han, Qian | Wang, Fuqiang | Cheng, Huamin | Wang, Haihua
The study investigated the occurrence of polycyclic aromatic hydrocarbons (PAHs) in the surface sediment from eleven sites in Yangpu Bay, China in December 2013 (winter) and July 2014 (summer). The 16 US EPA priority PAHs were found in the range of 1583.2–5701.7ng/g dry weights with an average of 3134.7±1241.3ng/g in winter and ranged from 2161.8 to 4527.2ng/g with an average of 3016.6±748.0ng/g in summer, respectively. The concentrations of the PAHs tended to be relatively high in comparison with other areas from the literatures. The identification using molecular indices analysis indicated that the PAHs originated mainly from pyrogenic and petrogenic sources in most of the sites. According to principle component analysis–multiple linear regression (PCA/MLR) for their source apportionment, the main sources of PAHs were vehicle emissions, petroleum products and biomass combustion. The risk assessment using international sediments quality guidelines and sediments quality criteria indicated that several PAHs, such as Nap, Flu, Phe, Ace, Acy and BghiP in most of the sites would potentially affect organisms in Yangpu Bay.
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